Reaction of methane with sulfur trioxide



Patented Jan. 3, 1950 REACTION OF METHANE WITH am I TRIOXIDE John C. Snyder, Burlington, and Arlaflll V. Grosse, Haveriord, Pa., assignors to Houdry Process Corporation, Wilmington; Del. a corporation of Delaware No Drawing. Application May 31, 1948, Serial No. 673,827

13 Claims. (Cl. 260-456) This invention relates to the utilization of light hydrocarbon gases and is particularly concerned 7 with the chemical transformation of such hydrocarbon gases to other chemical compounds.

An abundant source of light hydrocarbon gases, 8 reaction conditions such as temperature, and such as methane, is found in natural gas. relative concentration of reactants, and by the Natural gas consists principally of methane, genuse oi a catalyst. erally about to ethane, a few per cent of In accordance with the present invention, the inert non-hydrocarbon gases and a small amount reaction of methane with sulfur trioxide is of hydrocarbons boiling higher than ethane. l0 eil'ected under reaction conditions less severe than These higher boiling hydrocarbons may be rethose under which methaneis completely oxidized moved by compression or adsorption and marto the inorganic carbon oxides, carbon dioxide keted as liquefied gases, such as propane or and carbon'monoxide. Although the intention butane, or as natural gasoline. However, methane cl d s processes carried out without the use of a and ethan n t b transported i a 1:! catalyst, we have found that the reaction may be venient liquid form due to their low temperatures directed and accelerated, over a wide range of of liquefaction; hence these gases are generally temperatures and pressure conditions, by conused, other than for repressuring a gas or oil ducting the reaction in the presence of a whofield, only as fuel utilized at the origin or disnation catalyst and have found that a catalyst tributed by pipe lines. In a like manner, the 20 comprising a metal or a sulfate of a metal in methane and ethane content of refinery gases, group II-B of the periodic table, particularly such as those produced in connection with various mercury, is eiiective in catalyzing the reaction. cracking processes, has found little use except as We p r to mp oy reectifln temperatures above a cheap refinery fuel. Although natural gas and r om t mperatur pa t ula ly t mp ratures in gases of similar composition should furnish a 2 the range of 100 to 450 0-; Op r i n in onconvenient source of hydrocarbons for synthetic junction with a catalyst being esp c l y fl organic chemicals, the chemical utilization of tive Within s r The ot on D essuch material has, in the past, been hampered sures may be varied widely and include reaction by the lack of chemical reactivity of the principal pressures of atmospheric pressure and above, constituent, methane. Owing to this lack of the superatmospherlc pre es in n r ly chemical reactivity, previous attempts to convert and conveniently below 50 0 pounds per q re methane to derivatives, particularly oxygenated inch, such as pressures in' e range of 100 to derivatives such as methanol, have involved 2500 p n r Sq e inch- The relative either reactions feasible only under high pressure m n s f o y n ed 0r sulfonated derivaor such reactive reagents that the reaction was fives filmed in the t n y be varied by not controllable and hence proceeded past the varying the mol ratio of $03 to methane in the desired point. For example, when methane is reaction mixture although similar c s m y be oxidized by most reagents, either the yield of pr u e y varying other reaction conditions. oxidized products is too small to be commercially Thus. when more complete reaction or a high attractive or, under more drastic conditions, the 40 degree of sufonation of methane is desired, an reaction yields predominantly or only the highly excess of S0: (1. e., a moi ratio of S0: to methane oxidized products, carbon dioxide and carbon of greater th n One s a ly P f monoxide. whereas, when it is desired to favor the formation The general object of this invention is to pro-. of oxygenated products such as methanol in the vide novel processes for the utilization of light form of its esters or to favor the formation of hydrocarbon gases composed at least principally nionosulfonated products rather than dissulfoof methane by chemically transforming these nated products, the methane is generally prefhydrocarbon gases to organic derivatives. Other erably in excess. In practice, the effect of the objects will in part be obvious and in part aprelative concentration of methane and sulfur pear hereinafter. trioxide on the course ,0! the reaction will be In accordance with our invention, we react methane with sulfur trioxide to form considerable quantitles of at least one of the sulfonated or oxygenated organic derivatives of methane,

such as methanol, methane sulfonic acid, methl6 ionic acid, methyl esters of these suli'onic acids, methyl esters of sulfuric acid and the like. It has been found possible to vary the relative yields of products by the proper selection of balanced by economic considerations involved in the relative cost of the raw materials and in the relative value of the products, the expense involved in handling the materials processed and in obtaining the desired products from the reaction mixture. The invention includes the processing of light hydrocarbon gases consisting at least principally of methane such as natural gas or natural gas and similar gases from which any substantial amounts of propane and higher boiling constituents present have been removed to leave a fraction composed principally of methane in admixture with some ethane.

The sulfur trioxide for use in reactions of the present invention may be obtained from any source and there may be employed, for instance, sulfur trioxide obtained by heating oleum. When the reaction is effected under conditions that result in either partial or complete oxidation of any portion of the methane, some of the sulfur trioxide present is reduced to sulfur dioxide. In such cases, after the reaction of methane and sulfur trioxide has progressed to the desired extent, sulfur trioxide and sulfur dioxide may be separated from the reaction mixture and any residual sulfur trioxide used to convert further quantities of methane. If the sulfur trioxide content of a previously used mixture of sulfur oxides is too low for economic operation such a mixture may be fortified by the addition of more sulfur trioxide or the mixture may be mixed with air, oxygen or oxygen-containing gases and the sulfur dioxide catalytically converted wholly or partially to sulfur trioxide. Mixtures of sulfur oxides, having an appropriate concentration of sulfur trioxide,

may be reused; in which event sulfur dioxide, inert gases or sulfuric acid may be present. However, a gas prepared by catalytic oxidation of sulfur dioxide, as in the treatment of mixtures of sulfur trioxide and sulfur dioxide previously used for reaction with methane, may contain oxygen. Therefore, when using such a gas for reaction with methane, care must be exercised to avoid explosive concentrations of hydrocarbons and oxygen in the reaction mixture. To avoid such explosions, only sumcient oxygen to the mixture of sulfur oxides before conversion as to furnish non-explosive concentrations of oxygen in the converted gas, or the oxygen may be partially or wholly removed, as by combustion, or the hydrocarbons may be added in amounts outside the explosive limits.

Depending on the reaction conditions used,

methane and sulfur trioxide may react to form either sulfonated derivatives, such as methane sulfonic acid and methionic acid, or oxygenated derivatives, such as methanol although more highly oxygenated products such as formaldehyde or formic acid may also be formed under some conditions or both sulfonated and oxygenated derivatives may be formed. When both suli'onated' derivatives and methanol are formed, these reaction products may themselves react to form compounds such as methyl methane sulfonate, or

the methanol may react with sulfur trioxide or sulfuric acid contained in the reaction mixture to form a sulfuric acid ester. Although the production of carbon monoxide and carbon dioxide represent economically undesirable products, and conditions are generally chosen to reduce their production to a minimum, it may be sometimes desirable for other reasons to operate under conditions where a portion of the hydrocarbon material is so oxidized. In this case, water is present in the reaction mixture and sulfuric acid is consequently formed. As noted above, this sulfuric acid may then. react with methanol. Thus, depending on the reaction conditions, some or all of any alcohol formed may reactwith any sulfonic acids formed to produce esters of the sulmay be added fonic acids such as methyl methane sulfonate or methyl esters of methionic acid or may react with any sulfuric acid or sulfur trioxide present to give sulfates, such as methyl hydrogen sulfate or dimethyl sulfate. Although methanol formed may be converted immediately to the methyl sulfate esters, the methanol can be easily recovered because of the facility with which such esters can be hydrolyzed. In view of the above facts, when methanol is referred to herein, this term will be understood to include either free methanol or methanol in the form of a sulfuric acid ester.

At any event, the reaction products may be processed by conventional methods of separation such as preferential condensation or distillation at a suitable pressure. In this way, the reaction products may be separated into fractions containing one or more of the oxygenated, sulfonated and combined oxygenated-sulfonated products, or the separation can be carried further, with or without hydrolysis depending on the nature of the products, to yield individual compounds, such as free methanol. Alternatively, the reaction products may be first subjected to steam distillation under hydrolyzing conditions to obtain the methanol present in the reaction products both in the free state and as an ester. The residue of the hydrolysis may then be appropriately processed to obtain sulfonic acids.

Methyl methane sulfonate may be hydrolyzed to yield methanol and methane sulfonlc acid while the methyl esters of methionic acid can be similarly treated to obtain methanol and methionic acid which may then be hydrolyzed by well known methods to yield methane sulfonic acid.. Methane sulfonic acid thus produced may be thermally decomposed to sulfur dioxide and methanol as disclosed and claimed in our copending application Serial No. 673,628, filed May 31, 1946.

The invention includes effecting the reaction of sulfur trioxide and methane as a liquid, vapor, or mixed phase reaction. The relative amounts of the products formed in the reaction of sulfur trioxide with methane depend, among other factors, on the temperature employed; when the process is eflected at higher temperatures, such as temperatures in the range of approximately 250 to 325 C., the trend of product composition is towards a relatively high content of oxygenated products such as methanol without uneconomical formation of carbon oxides while at lower temperatures, such temperatures in the range of 200 to 250 C.,-the trend is towards a relatively high content of sulfonated products. Short contact times and higher temperatures such as a range of 300 to 400 C. may be used for the production of oxygenated products where it is desired to increase the reaction rate.

In order to illustrate processes embodying the present invention, but not to be construed as limiting the practice thereof, the following examples are given:

Example I Sulfur trioxide and methane were reacted in a closed vessel under the following conditions:

Temperature of reaction 263 C.

Time of reaction 1 hour Mol ratio of S0: to CH4 10 Pressure (maximum) 960 lbs/sq. in.

present had been converted to such organic derivatives.

Example II Example HI Sulfur trioxide and methane were reacted in a closed vessel under the following conditions:

Temperature of reaction 240 C.

Time of reaction 0.75 hours Mol ratio of S03 to CH4 2.4

M01 ratio of HgSOr to CH4 0.01 Pressure (Maximum) 830 lb./sq. in.

Analysis of the liquid reaction products indicated that 8% of the methane originally present had reacted to form methanol and 18% of the methane had reacted to form sulfonated derivatives of methane.

Example IV Liquid products from the reaction of methane with sulfur trioxide were obtained from several runs made under the following conditions (approximate):

Time of reaction 1.5 hours Temperature 260 C.

Mol ratio of S: to CH4 2.1

M01 ratio of HgSO4 to CH4 0.011 Pressure (maximum) 840 lbs/sq. in.

Analysis of the liquid reaction products indicated that, based on the methane originally present, about 9% of the methane had been converted to methane sulfonic acid, about 33% to methionic acid and about 2.4% to methanol which was present in the reaction mixture in the ester form.

Example V A run, reacting sulfur trioxide and methane as described above, was made under the following conditions:

Temperature 300 C.

Time of reaction 40 minutes M01 ratio of $03 to CH4 6.9

Catalyst HgSO4 Pressure (maximum) 1350 lbs/sq. in.

The liquid reaction products were analyzed and showed that about 28% of the methane originally present was converted to methanol, which was present in the reaction mixture in the ester form, whereas a smaller amount, about 17%, was converted to methane sulfonic acid.

Example VI A run, reacting sulfur trioxide and methane as described above, was made under the following conditions:

Time of reaction 1.5 hours Temperature 230 C.

Mol ratio of S03 to CH4 0.59

Catalyst HgS04 Pressure (maximum) 820 lbs./sq. in.

Analysis of the liquid products indicated that, of the original methane present, about 4% had been converted to methanol present in the reaction mixture in the form of methyl esters, about 2.5% to methane sulfonic acid, and about 4% to methionic acid.

In the above description, the reaction between sulfur trioxide and methane, is, at times, discussed on the basis that the formation of methanol by this reaction is a two step process (1. e., a first step of sulfonation, followed by a second step of pyrolysis of the sulfonated derivative). It is to be understood that the postulatlon of such a two step process is not intended to exclude the possibility of a single step process in which the methane is oxidized to methanol directly but is used because it is convenient when discussing the overall reactions. Any mechanism of reaction should not be construed as a limitation on the present invention. Furthermore, it is to be noted that a similar result (the formation of methanol) is accomplished by either a two step or a single step process, and that in the latter process, although the methane may be directly oxidized to methanol without the intermediate formation of a sulfonated derivative, sulfonated products may be produced by another competing reaction, occurring simultaneously. In the above description and in the appended claims, the term, organic derivative of methane, is used as a term for those derivatives of methane in which at least one hydrogen attached to methane is not replaced, in contradistinction to what might be termed the inorganic oxidation products of methane; viz., carbon monoxide and carbon dioxide.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim as our invention:

1. In the preparation of organic derivatives of methane, the process which comprises reacting a reaction mixture comprising methane and sulfur trioxide in the presence of mercury sulfate at temperatures in the range of 200 to 325 C. and at reaction pressures in the range of to 2500 pounds per square inch.

2. The process which comprises sulfonating methane to form a sulfonated derivative of methane in the presence of a catalyst selected from the group consisting of metals and sulfates of metals in group II-B of the periodic table at temperatures of at least about 100 C. and below 250 C.

3. In the chemical production of organic derivatives of methane, the process which comprises reacting a reaction mixture comprising methane and sulfur trioxide in the presence of mercury sulfate at temperatures in the range of 200 to 325 C. and at superatmospheric pressures to form reaction products comprising at least one of the organic derivatives of methane, and separating at least one of said organic derivatives of methane from said reaction products.

4. In the preparation of organic derivatives of methane, the step which comprises reacting methane and sulfur trioxide at temperatures in the range of 100 to 450 C. and at reaction pressure of at least atmospheric pressure in the presence of a catalyst selected from the group consisting of metals and sulfates of metals in group II -B of the periodic table.

5. The process which comprises forming at least one compound selected from the group consisting of methane sulfonic acid, methionic acid,

acoaoaa sisting of metals and sulfates of metals in group II-B of the periodic table.

6. The process which comprises forming methane sulfonic acid by reacting methane and sulfur trioxide in the presence of a catalyst selected from the group consisting of metals and sulfates of metals in group 11-3 of the periodic table.

7. The process which comprises forming methionic acid by reacting methane and sulfur trioxide in the presence of a catalyst selectedfrom the group consisting of metals and sulfates of metals in group 11-3 of the periodic table.

8. The process which comprises forming a methyl ester of a sulfonic acid of methane by reacting methane and sulfur trioxide in the presence of a catalyst selected from the group consisting of metals and sulfates of metals in group IIB of the periodic table.

9. In the preparation of organic derivatives of methane, the step which comprises reacting methane and sulfur trioxide at temperatures in the range of 100 to 450 C. and at reaction pressure of at least atmospheric pressure in the presence of a catalyst selected from the group consisting of metals and sulfates of metals in group II-B of the periodic table to form products comprising methane sulfonic acid and separating methane sulfonic acid from said products.

10. In the preparation of organic derivatives of methane, the step which comprises reacting methane and sulfur trioxide at temperatures in the range of 100 to 450 C. and at reaction pressure of at least atmospheric pressure in the presence of a. catalyst selected from the group consisting of metals and sulfates of metals in group 1IB of the periodic table to form products comprising methionic acid and separating methionic acid from said products.

11. In the preparation of organic derivatives of methane, the step which comprises reacting methane and sulfur trioxide at temperatures in the range of to 450 C. and at reaction pressure of at least atmospheric pressure in the presence of a catalyst selected from the group consisting of metals and sulfates of metals in group 11-3 of the periodic table to form products com-- prising a methyl ester of a sulfonic acid of methane and separating a methyl ester of a sulfonic acid of methane from said products.

12. The process which comprises forming at least one compound selected from the group consisting of methane sulfonic acid, methionic acid, methyl esters of sulfuric acid, methanol and methyl esters of sulfonic acids of methane by reacting methane and sulfur trioxide in the presence of mercury sulfate.

13. In the preparation of organic derivatives of methane, the step which comprises reacting methane and sulfur trioxide at temperatures in the range of 100 to 450 C. and at reaction pressure of at least atmospheric pressure in the presence of mercury sulfate.

JOHN C. SNYDER. ARISTID V. GROSSE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,094,451 Guenther Sept. 28, 1937 2,383,752

Sveda Aug. 28, 1945 OTHER REFERENCES 

5. THE PROCESS WHICH COMPRISES FORMING AT LEAST ONE COMPOUND SELECTED FROM THE GROUP CONSISTING OF METHANE SULFONIC ACID, METHIONIC ACID, METHYL ESTERS OF SULFURIC ACID, METHANOL AND METHYL ESTERS OF SULFONIC ACIDS OF METHANE BY REACTING METHANE AND SULFUR TRIOXIDE IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF METALS AND SULFATES OF METALS IN GROUP II-B OF THE PERIODIC TABLE. 